The instant invention generally relates to a process for the production of a protein product and more specifically to a soybean protein product of improved flavor characteristics.
This invention was conceived and developed largely for soy materials because of the special problems encountered with such materials. Therefore, it will be explained largely with respect to soy materials, and has special application to such materials, although it can be used for other oilseed protein materials in the broader aspects of the invention.
Generally, in the use of protein products derived from vegetable protein sources such as soybeans, the biggest problem in achieving wide acceptance of these products is the presence of an inherent "beany" flavor and odor. Even with various processing techniques which involve the purification and isolation of the protein from soybeans, these procedures are unable to completely eradicate this characteristic "beany" flavor. Furthermore, although a rendered protein product may apparently lack this characteristic odor, when the protein product is included in a food product such as a milk or beverage and heated, this undesirable flavor has a tendency to reappear, thus requiring a high percentage of strong flavorants to completely mask the "beany" taste. Therefore, although various processing techniques have been partially successful in eliminating this undesirable flavor from protein products derived from soybeans, nevertheless a need still exists for a solution to this problem.
One of the more common products derived from vegetable protein sources such as soybeans, is referred to as a "protein isolate" in that most of the available protein is isolated to yield a product having a protein content on the order of 95 percent or higher. The basic process for producing the isolate comprises dispersing ground, defatted soybeans in a strongly alkaline solution, followed by the addition of acid to lower the pH of the extract to the isoelectric point of the protein, which is between about 4 and 5. The precipitated protein or curd is then collected and the whey or excess liquor discarded, after which it is washed and may be dried, if desired, by spray drying or similar techniques. Even after this extensive degree of processing, the soy protein isolate for the most part, suffers from the flavor problems noted above.
As previously noted, there have been various attempts to improve the flavor of soybean isolates, and at the same time, decolorize them as much as possible. The whiter the product, the more desirable it is in the formulation of simulated milks, or as a whitener for coffee, or as a fortifying protein source for food products in general. Generally, however, while a single prior art process might have been more successful than another in eliminating undesirable flavor, it would correspondingly suffer from a deficiency with regard to color, therefore, requiring additional processing to eliminate this.
Various prior art processes have employed absorbants such as fullers earth, clay, or activated carbon in an attempt to decolorize proteins. For example, U.S. Pat. No. 3,493,385 suggests the treatment of protein hydrolysates with activated carbon to remove color, while U.S. Pat. No. 1,165,199 suggests that bone black can be used to lighten soy milk and U.S. Pat. No. 2,397,307 suggests that soy protein can be decolorized with activated carbon. In the latter two situations, however, it is specifically indicated that either the addition of flavorants is needed, or that decolorizing by this route has failed to produce a protein of the necessary quality and light color. Therefore, no one has successfully employed activated carbon to successfully deflavorize, decolorize and deodorize the soy protein or any of its proteinaceous extracts.
The present invention is also concerned with the removal of impurities, from various other vegetable oilseed materials. Techniques have been shown in prior art processes for the removal and detoxification of aflatoxins from oilseed material. U.S. Pat. No. 3,493,385 suggests the use of a short-arc mercury lamp to detoxify aflatoxin while U.S. Pat. No. 3,515,736 suggests that aflatoxin can be extracted from peanut meal with an azeotropic mixture of acetone, hexane and water. No one has suggested the use of activated carbon to remove aflatoxins from oilseed material such as peanut and cottonseed meal.